SEASONAL DYNAMICS OF A LEECH-MYSID SHRIMP INTERACTION IN A TEMPERATE SALT MARSH

¹ Dept. of Biology and The Wetlands Institute, Lehigh University, Bethlehem, PA 18015

The spatial and temporal distributions and aspects of the life history of the marine leech, Mysidobdella borealis, were studied in a salt marsh embayment and adjacent ocean area in southern New Jersey, U. S. A. Mysid hosts, Neomysis americana, occurred in all epibenthic sled collections, but leeches were only collected in the embayment in winter and spring. Leeches were in the cooler ocean areas during the summer. The recurrence of M. borealis in the embayment in November or December coincided with the migration of large mysids from the ocean. Leeches reproduced in the marsh each spring, but no life stages were collected after embayment temperatures reached 20°C. Laboratory experiments demonstrated that adult and newly hatched M. borealis were killed by long exposures to temperatures greater than 20° C. The recruitment and survival of the borealarctic leech in estuaries at the southern extent of its geographical range is determined by host migration and water temperature.